Radiotelephone communication systems are known which include a plurality of relay bases (also called base stations) installed in fixed locations, connected to a telephone network, and intended to provide radio links with a series of mobile stations moving within a territory covered by the radiotelephone communication system. In known systems, a relay base comprises at least one receive antenna for receiving radio signals; a receiver coupling member connected to the receive antenna; a series of receiver members connected to the receiver coupling member; a series of digital processing units connected to respective ones of the receiver members, to a line of a telephone network, and to a control unit; a series of transmitter members connected to the digital processing units; a transmitter coupling member connected to the transmitter members; and a transmit antenna connected to the transmitter coupling member.
In addition, in order to provide security of transmission between the base station and the mobiles, regardless of the radio obstacles that may exist between the base station and the mobiles, e.g. unfavorable configurations of terrain or various structures constituting radio screens, it is known to be desirable to transmit using frequency hopping, with each frequency being affected differently by the radio obstacles.
In order to preform frequency hopping using existing bases having the structure outlined above, it is necessary for the transmitter coupling member to be a wideband member operating in hybrid mode. Such coupling members suffer from the drawback of giving rise to power losses that are a function of the number of stages of the base, such that it is necessary to provide very large amounts of initial power at bases for relaying a large number of calls simultaneously.
In order to reduce the power required while still providing frequency hopping, proposals have been made to group together receiver members and transmitter members in common modules associated with coupling operating in a cavity mode. However, such a system requires an extremely complex switching matrix to be installed for providing the links between the transmitter/receiver modules and the digital processing units.
An object of the present invention is to provide a relay base which is relatively simple in structure and capable of operating easily in association with a transmitter coupling member of the wideband or cavity type.